This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Infants of inborn errors of bile acid metabolism represent a relatively heterogeneous group of patients with a variety of clinical manifestations. They can range from neonatal cholestasis and severe liver injury in the neonate to fat-soluble vitamin deficiency and its manifestations in the older child or even end-stage cirrhosis in later childhood. Using techniques of mass spectrometry including fast atom bombardment on urine samples, electron microscopy and MRI-spectroscopy, we have identified and evaluated a growing group of infants and children with these disorders.